JP3261765B2 - Optical cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable having high resolution characteristics when used as a temperature sensor or the like.

[0002]

2. Description of the Related Art In recent years, a system has been put to practical use in which an optical fiber is stretched and temperature and its position information are simultaneously measured to detect a temperature distribution. By the way, the temperature information when an optical fiber is used as a temperature sensor indicates the average temperature in a certain section in principle. That is, when the optical fibers are laid in a straight line, it is impossible to obtain a distance resolution within a certain section. Therefore, the optical fibers are arranged spirally as shown in FIG. 3, and the length of the optical fibers per length of the object to be measured is increased to increase the distance resolution. For example,
The optical fiber 1 is wound around the core 5 as shown in FIG. 3 and embedded in the ground to measure the temperature distribution in the ground, or as shown in FIG. 4, a spacer 7 having a spiral groove 6 on the surface. A spacer type cable in which the optical fiber 1 is introduced into the groove is used.

[0003]

A cable in which an optical fiber is wound around a core cannot sufficiently protect the optical fiber from an external force, and often causes an increase in transmission loss. Further, there is a problem that the position of the optical fiber is shifted and accurate position information cannot be obtained. On the other hand, the spacer type cable has high rigidity, has a limitation on a bending radius, and has a drawback that, due to its structure, its thermal response is poor and its application range is limited. Therefore, an object of the present invention is to provide an optical cable that solves these problems.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a tube formed by bending both edges of a metal tape and spirally engaging one edge and the other edge, and a tube formed at an engaging portion of the tube. This is an optical cable provided with a gap and an optical fiber introduced into the gap.

[0005]

According to the above construction, in the optical cable of the present invention, the optical fiber is introduced into the gap formed at the engagement portion of the spirally engaged tube. Therefore, the engaging portion can be slid so that the cable is highly flexible. Since the optical fiber is housed in the air gap, its position is fixed, and the structure is tough against external force.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing the configuration of the present embodiment.
Both edges of the metal tape 2 are bent in the opposite direction in a corrugated manner, and one edge is spirally engaged with the other edge to form the tube 1. At this time, a gap 3 determined by the shape and size of the waveform is formed. When the tape 2 is spirally engaged, the optical fiber 4 is introduced into the gap. FIG. 2 is a sectional view of an optical cable in which an optical fiber is applied to a tube in which a mating portion is formed more firmly, and has the same operation and effect as in FIG.

[0007] The optical cable thus formed can be bent without difficulty because the tapes slide on each other at the mating portion, and the position of the optical fiber is not shifted since the optical fiber is introduced into the gap. The size of the gap 3 and the pitch of the spiral tube 1 are determined by the width, waveform and dimensions of the tape 2 and can be selected to desired values. Therefore, the distance resolution of the temperature sensor can be set to an arbitrary value by the diameter of the spiral tube 1 and the above-mentioned pitch. Metal tape 1
In general, stainless steel is used from the viewpoint of strength and corrosion resistance, but when used as a temperature sensor, copper having excellent thermal conductivity is suitable. Also, titanium is heat resistant,
Has excellent corrosion resistance.

Further, by using the optical fiber in a metal tube, the protection from external force is enhanced, and a waterproof structure can be obtained. The case where the present invention is applied to a sensor cable has been described above, but the present invention is not limited to this and can be used as a normal optical cable.

[0009]]

As described in detail above, the optical cable of the present invention has an optical fiber introduced into a gap formed in a mating portion of a spirally meshed tube. Therefore, the engaging portion can be slid so that the cable is highly flexible. Since the optical fiber is housed in the air gap, its position is fixed, and the structure is tough against external force.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the configuration of the present embodiment.

FIG. 2 is the same as FIG.

FIG. 3 is a perspective view showing a configuration of a conventional optical cable.

FIG. 4 is a cross-sectional view showing a configuration of a conventional optical cable.

[Explanation of symbols]

 1: spiral tube 2: metal tape 3: void 4: optical fiber 5: core 6: spiral groove 7: spacer 8: sheath

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-66134 (JP, A) JP-A-61-66133 (JP, A) JP-A 4-48506 (JP, U) JP-A 61-66133 57709 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 6/44 G01K 11/12 G01D 5/36

Claims (1)

(57) [Claims] 1. A tube formed by bending both edges of a metal tape and spirally meshing one edge with the other edge, a gap formed at a meshing portion of the pipe, and a pipe introduced into the gap. An optical cable comprising: an optical fiber;